ALSA: usb-audio: Get UMP EP name string from USB interface

USB descriptor may provide a nicer name for USB interface, and we may
take it as the UMP Endpoint name.  The UMP EP name is copied as the
rawmidi name, too.

Also, fill the UMP block product_id field from the iSerialNumber
string of the USB device descriptor as a recommended unique id, too.
Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20230523075358.9672-11-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/midi2.c

@@ -892,15 +892,39 @@ static int set_altset(struct snd_usb_midi2_interface *umidi)
 				 umidi->hostif->desc.bAlternateSetting);
 }
 
+/* fill UMP Endpoint name string from USB descriptor */
+static void fill_ump_ep_name(struct snd_ump_endpoint *ump,
+			     struct usb_device *dev, int id)
+{
+	usb_string(dev, id, ump->info.name, sizeof(ump->info.name));
+}
+
 /* fill the fallback name string for each rawmidi instance */
 static void set_fallback_rawmidi_names(struct snd_usb_midi2_interface *umidi)
 {
+	struct usb_device *dev = umidi->chip->dev;
 	struct snd_usb_midi2_ump *rmidi;
+	struct snd_ump_endpoint *ump;
 
 	list_for_each_entry(rmidi, &umidi->rawmidi_list, list) {
-		if (!*rmidi->ump->core.name)
-			sprintf(rmidi->ump->core.name, "USB MIDI %d",
-				rmidi->index);
+		ump = rmidi->ump;
+		/* fill UMP EP name from USB descriptors */
+		if (!*ump->info.name && umidi->hostif->desc.iInterface)
+			fill_ump_ep_name(ump, dev, umidi->hostif->desc.iInterface);
+		else if (!*ump->info.name && dev->descriptor.iProduct)
+			fill_ump_ep_name(ump, dev, dev->descriptor.iProduct);
+		/* fill fallback name */
+		if (!*ump->info.name)
+			sprintf(ump->info.name, "USB MIDI %d", rmidi->index);
+		/* copy as rawmidi name if not set */
+		if (!*ump->core.name)
+			strscpy(ump->core.name, ump->info.name,
+				sizeof(ump->core.name));
+		/* use serial number string as unique UMP product id */
+		if (!*ump->info.product_id && dev->descriptor.iSerialNumber)
+			usb_string(dev, dev->descriptor.iSerialNumber,
+				   ump->info.product_id,
+				   sizeof(ump->info.product_id));
 	}
 }